1. Field of the Application
This application is in the field of application of RF power onto processing chambers so as to maintain plasma therein and, more specifically, for controlling the tuning of an RF matching circuit to minimize reflecting power.
2. Related Art
Various processing chambers are known in the art which utilize plasma for fabrication of semiconductor devices, flat panels, solar cells, etc. An example of such chambers include etch, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), metal organic chemical vapor deposition (MOCVD), vapor phase epitaxy (VPE), etc. In such chambers, an RF power source provides RF power at a prescribed frequency and power. The RF power is applied to an electrode or an antenna via an RF matching network. The RF matching network is designed to tune the transmission line to match the chamber's impedance so as to efficiently deliver the RF power to the chamber.
One problem of the prior art is that the chamber's impedance drifts or changes. For example, component aging and chamber condition, such as cleanliness, may lead to impedance drifting. Also, following preventive maintenance the chamber's impedance may change. Additionally, different substrates may lead to change in chamber's impedance. Accordingly, there is a need to monitor the chamber's impedance and tune the RF matching network to minimize reflective power and ensure efficient delivery of the RF power.
On the other hand, the various chambers and systems in the fabrication facility (fab) are generally controlled by a central host running production management software. In such an environment, once a recipe is qualified for a given system, it is stored on the central host. The host then operates the system according to the stored recipe. This recipe is not allowed to be changed without re-qualification. That is, if the recipe needs to be changed, due to, e.g., changes in the condition of the chamber, the changed recipe must be re-qualified before it is allowed to replace the old recipe. This is time and resource consuming activity, which fab managers would prefer to avoid.
However, when the chamber impedance changes or drifts, the recipe may need to be changed to correct for the impedance change. Accordingly, what is needed is a method and system enabling executing reactive measures to impedance drift or change without changing the stored recipe.